In the absence of antiretroviral therapy (ART), HIV-1 infection is typically followed by declining CD4+ T-cell counts, elevated viral loads, and eventual progression to AIDS and death. By means of incompletely understood mechanisms, a minority of individuals maintain plasma viral loads under the clinical limit of detection (50 copies/mL) ove the long term, even without ART. A better understanding how these elite suppressors or controllers (ES) restrain virus replication may aid in developing effective vaccines and new treatments. A class of small regulatory molecules-short nucleic acids known as microRNAs (miRNAs)- provide an only recently discovered layer of post-transcriptional regulation. miRNAs are also exported from the cell in a specific fashion and are sufficiently stable in blood to establish cell-to-cell communication. Despite intense interest in these molecules and productive findings in multiple fields of study, there is relatively little information on cellular or extracelular miRNA involvement in HIV-1 control and progression, and virtually none on miRNAs in ES. We recently published the first report of plasma miRNA biomarkers of infection and CNS disease in a primate model of HIV disease, as well as the first study of miRNAs in the ES population, in which we found that PBMC miRNAs cluster chronic progressors from healthy controls while suggesting that more than one mechanism may underlie the ES phenomenon. These results, combined with the findings by our group and others of qualitative and quantitative differences in T-cell subsets of ES, chronic progressors, and controls, have prompted us to propose this project. We aim to characterize miRNA associations with elite suppression, normal progression of HIV-1 infection, and the response to ART. We hypothesize that: 1) there exist specific cellular and plasma miRNA biomarkers of ES, HIV progression, and response to ART; 2) miRNAs are involved in pathways that contribute virus control and render ES cells resistant to HIV-mediated cell death; and 3) extracellular miRNAs are nonuniformly distributed among size- and functionally distinct plasma particles, indicating specific release and involvement in immune coordination networks. To test these hypotheses, we will collect samples from a well-characterized ES cohort, ART-treated and ART-nave chronic progressors, and healthy controls. In Aim 1, we will analyze levels of miRNAs in six specific immune cell types that are involved in elite suppression and HIV replication: CD4+ and CD8+ nave, effector memory, and central memory cells. This aim will also examine the relationship of miRNA profiles and classical parameters of HIV disease. In Aim 2, we will characterize extracellular plasma miRNAs, which circulate in vesicles, lipoprotein particles, and protein complexes, and determine whether specific plasma miRNAs are associated with abundance and/or size of plasma nanoparticles that derive from CD4+ or CD8+ T-cells. The findings of this project will have relevance for basic miRNA science and will advance HIV-1 clinical science through biomarker discovery and determining the feasibility of miRNA-based therapies based on the ES phenomenon.